1. Technical Field
The present invention relates to an electron emission device and, more particularly, to a structure of an electron emission region of the electron emission device.
2. Related Art
The different types of electron emission devices that use cold cathodes as electron emission regions include the field emitter array (FEA) type, the surface conduction electron emitter (SCE) type, and the metal/insulation layer/metal (MIM) type. In the case of the FEA type, materials that emit electrons with the application of an electric field are used as the electron emission region. The emitted electrons strike a phosphor layer to generate light. The overall quality of the FEA type is heavily dependent on the characteristics of the electron emission regions.
In the FEA type initially developed, molybdenum (Mo) was used as the material for the electron emission regions, and a conical configuration ending in a sharp point and having a size in the range of micrometers was employed. An example of such a conventional technology is disclosed in U.S. Pat. No. 3,789,471, which discloses a display device including field emission cathodes.
However, a serious drawback of the conventional electron emission region configuration is that it is necessary to use semiconductor processes to produce conical electron emission regions. This makes manufacturing difficult and reduces productivity. In addition, it is difficult to obtain uniform quality throughout the device as the substrate size is enlarged, making the conventional electron emission region structure unsuitable for application to devices with large sizes.
Therefore, those involved with FEA type manufacture and research are developing ways to form electron emission regions using a thick-layer process, such as screen printing, and are also using a carbon-based material capable of realizing favorable electron emission, even at low voltage driving conditions of approximately 10˜50V. Examples of such carbon-based materials include graphite, diamond, diamond-like carbon, and carbon nanotubes. Also, nanometer-sized materials which may be used as electron emission regions include nano-tube, nano-wire and nano-fiber. Among these, nano-tubes, and especially carbon nano-tubes, appear to be very promising for use as electron emission regions because of their extremely minute tips (i.e., a radius of curvature of approximately 100 Å), and because carbon nanotubes are able to emit electrons in low electric field conditions of about 1˜10V/μm.
Examples of conventional cold cathode FEAs utilizing carbon nano-tubes are disclosed in U.S. Pat. Nos. 6,062,931 and 6,097,138.
In the case wherein an FEA type employs what is referred to as a triode structure, including cathode electrodes an anode electrode, and gate electrodes, a top-gate structure may be used. In the top-gate structure, the cathode electrodes are first formed on a substrate, the electron emission regions are formed on the cathode electrodes, and the gate electrodes are then mounted on the electron emission regions.